Scoters and other birds feeding on purple varnish clams: Some observations at Spanish Banks, Vancouver, British Columbia

J. M. Ryder

3415 West 24 Avenue, Vancouver, B.C. V6S 1L3

Abstract: An unusually large number of Surf Scoters (Melanitta perspicillata) and White-winged Scoters (M. fusca) were observed diving and feeding on the introduced purple varnish clam (Nuttallia obscurata) along Spanish Banks, Vancouver, in February 2006. At low tide, gulls and crows were seen consuming clams they found exposed and dying on the beaches. Features observed in the beach sand and meteorological records suggest that erosion of beach sand and resulting exposure of the clams to sub-zero temperatures resulted in clam mortality and a sudden abundance of readily accessible food for the birds. This is one of the first recorded cases of sea ducks preying on this introduced clam. Some introduced molluscs concentrate contaminants from the local environment and pass them up the food chain to waterfowl. The potential effects of varnish clam consumption by sea ducks are not yet known.

Key words: Vancouver, British Columbia, Spanish Banks, Surf Scoter, Melanitta perspicillata, White-winged Scoter, M. fusca, purple varnish clam, Nuttallia obscurata

PDFicon Ryder, J.M. 2007. Scoters and the other birds feeding on purple varnish clams: some observations at Spanish Banks, Vancouver, British Columbia. British Columbia Birds 16:24-27.


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